A-M baby

Task/Factorial/Scheme/factorial-1.ss

@@ -0,0 +1,4 @@
+(define (factorial n)
+  (if (<= n 0)
+      1
+      (* n (factorial (- n 1)))))

Task/Factorial/Scheme/factorial-2.ss

@@ -0,0 +1,6 @@
+(define (factorial n)
+  (let loop ((i 1)
+             (accum 1))
+    (if (> i n)
+        accum
+        (loop (+ i 1) (* accum i)))))

Task/Factorial/Scheme/factorial-3.ss

@@ -0,0 +1,4 @@
+(define (factorial n)
+  (do ((i 1 (+ i 1))
+       (accum 1 (* accum i)))
+      ((> i n) accum)))

Task/Factorial/Scheme/factorial-4.ss

@@ -0,0 +1,23 @@
+;Using a generator and a function that apply generated values to a function taking two arguments
+
+;A generator knows commands 'next? and 'next
+(define (range a b)
+(let ((k a))
+(lambda (msg)
+(cond
+	((eq? msg 'next?) (<= k b))
+	((eq? msg 'next)
+	(cond
+		((<= k b) (set! k (+ k 1)) (- k 1))
+		(else 'nothing-left)))))))
+
+;Similar to List.fold_left in OCaml, but uses a generator
+(define (fold fun a gen)
+(let aux ((a a))
+	(if (gen 'next?) (aux (fun a (gen 'next))) a)))
+
+;Now the factorial function
+(define (factorial n) (fold * 1 (range 1 n)))
+
+(factorial 8)
+;40320